Dr Hilary Jones has urged Britons to take vitamin D deficiencies seriously this winter, particularly as a cold snap brings freezing temperatures across the country.
The ITV doctor, who appears regularly on Good Morning Britain, said the significant increase in vitamin D deficiencies in the winter months can lead to other health problems, such as higher risk of catching COVID-19 and other viruses.
His warning comes after the British Medical Association warned that the forthcoming season will be the "worst winter on record" for health services, as there are "record numbers of patients waiting for care and treatment".
Britons tend to be at higher risk of vitamin D deficiencies in the winter as shorter days mean less sunlight. Regular sun exposure is the main way the body creates this vitamin, which is essential for bones and teeth, as well as the immune system.
A lack of vitamin D has also been linked to depression, as not getting enough of it can lead to mood disorders. In the dark winter months, when we don't get enough sunlight, many people become vulnerable to seasonal affective disorder (SAD).
Dr Jones said: "Vitamin D plays a crucial role in your health - both physically and mentally. The colder months see a huge rise in vitamin D deficiencies, which leads to higher illness rates alongside depression due to the lack of sunlight."
According to Dr Jones, not getting enough vitamin D can lead to a series of health issues.
These include:
Vitamin D plays a key role in overall health, helping the body to fight off bacteria and viruses by stimulating our immune systems.
Exposure to sunlight helps our bodies to produce vitamin D, which is necessary for our brains to produce serotonin, also known as the 'happy chemical'.
Vitamin D helps regulate our immune system, in turn helping to prevent infections.
Vitamin D plays a role in the production of melatonin, which helps us sleep. Without melatonin, you could be at risk of not just fatigue, but also insomnia.
Low levels of vitamin D greatly increases a person's risk of muscle strength loss.
Dr Jones, in partnership with Newfoundland Diagnostics, has provided three top tips for increasing your vitamin D intake this winter, in order to avoid health issues related to a lack of it.
"Look to incorporate the 'sunshine vitamin' into your diet via foods. [This can include] oily fish, such as salmon and mackerel, or fortified foods like certain breakfast cereals and plant-based milks."
"We know vitamin D is important for good immune health, and there are many people who are deficient in vitamin D, who should be taking a supplement as recommended by the World Health Organisation (WHO) and NHS.
"As there isn't enough sunlight in this part of the world for our bodies through winter to make sufficient amounts, supplements become increasingly important."
Dr Jones said that many of us became familiar with self-testing during the pandemic, and recommended keeping up the habit during the colder months.
"With GP appointments becoming increasingly hard to obtain in a hurry, getting into the habit of regular self-monitoring with DIY testing is a good idea, especially for vitamin D deficiency - an often-missed side effect of shorter days and longer nights."